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BMW P0597: thermostat heater control circuit open
An electrical fault in the heating element that lets the engine computer open the thermostat early. Wiring or the thermostat itself.
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Codes on this page
| Code | Definition | Source |
|---|---|---|
| P0597 | Thermostat heater control circuit open | Generic OBD-II |
| 1D2404 | Characteristic map thermostat, actuation: line disconnection | SI B11 18 16 (PDF) |
| 1D2401 | Characteristic map thermostat, actuation: short circuit to B+ | SI B11 18 16 (PDF) |
| 1D2402 | Characteristic map thermostat, actuation: short circuit to ground | SI B11 18 16 (PDF) |
P-codes are the generic OBD-II codes any reader shows. Six-character and four-character hex codes are BMW's own, read with a BMW-capable scanner; the wording is BMW's, from the source shown.
What it means
BMW's map-controlled thermostat has a heating element the DME switches on to open it sooner under load. P0597 on a generic reader, or 1D2404 on a BMW scanner, means that circuit is open. BMW's own fault texts for the same actuation circuit also cover shorts to power and ground.
Can I keep driving?
Usually yes; watch the temperature. The thermostat still works mechanically, so most cars drive normally. If an overheating message appears, stop and let the engine cool.
Usual causes on BMWs
| Cause | Cars most affected | What you notice | Evidence | Repair prices (national average) |
|---|---|---|---|---|
| Damaged thermostat wiring insulation letting coolant in | F48 X1 with B46/B48 (bulletin) | Check engine light, sometimes "Engine overheated" or "Exercise caution!". BMW removes the alternator bracket and water pump/thermostat to check for corrosion. | SI B11 18 16 (PDF) | — |
| Thermostat heating element failed | N52, N54, N55, N20, B46/B48, B58 | Usually fixed by replacing the thermostat (on N5x engines it is part of the water pump job; on B58 it's the heat management module). | — | N52 / N54 / N55 electric water pump + thermostat Indie $758–$1,259 Dealer $1,841–$2,250 B58 heat management module (thermostat) replacement Indie $978–$1,506 Dealer $2,234–$3,037 |
A bulletin isn't a recall and doesn't mean your car has the problem; open it for the exact models and build dates. Estimates are national averages built from BMW warranty labor time, regional shop rates and parts prices; open a repair for your ZIP. "Owners paid" is the middle half of sourced prices, shown where we have at least 3.
What to do
- Ask the shop to check the connector and wiring for corrosion or coolant before replacing parts.
Warnings it can bring up
Engine overheating or coolant warning Check engine light, no message
Related codes
Other BMW bulletins that mention it
- SI B12 13 16 Thermostat check engine light G11, G12 · Feb 2018
2 of the BMW bulletins we hold mention it in their text; these are the closest matches.
Sources
Bulletins are cited in the tables above. Explanations are ours; where a source is an owner report rather than BMW, it is labelled as one.